Bug 2520649 (CVE-2026-76641)

Summary:	CVE-2026-76641 expat: Expat: Denial of Service via XML external entity parsing
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	akhatavk, aos-team-art-private, asdas, dpaolell, gotiwari, jdelft, jhorak, jupierce, lgarciaa, mbiarnes, mvyas, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
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Doc Text:	A flaw was found in Expat. Attackers can exploit an out-of-bounds read vulnerability by processing XML with external entity parsers created via XML_ExternalEntityParserCreate. This can lead to memory corruption. Specifically, a mismatch in struct sizes can cause a read past memory boundaries, potentially resulting in a denial of service (DoS) due to a segfault or incorrect handling of XML attributes.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2540058, 2540060
Bug Blocks:

Description OSIDB Bzimport 2026-08-20 17:57:06 UTC

Expat through 2.8.3 contains an out-of-bounds read vulnerability that allows attackers to trigger memory corruption by processing XML with external entity parsers created via XML_ExternalEntityParserCreate. A struct size mismatch between ELEMENT_TYPE members causes storeAtts to read the attIndex member past allocated memory boundaries, resulting in failure to normalize whitespace in non-CDATA attributes or a wild pointer dereference causing a segfault. This vulnerability was introduced by the fix for CVE-2026-66046.